Gas-lift valve and method of use

ABSTRACT

A gas-lift valve comprising an elongated vertically orientated tubular body with inlet ports positioned for communication with the inlet ports of a gas-lift valve mandrel, a valve seat and valve port at the upper end of the valve body, a movable gas charged dome positioned within the body below the valve seat, a valve ball assembly attached to the dome, and a collapsible bellows positioned to move the dome and manipulate the valve ball assembly downward onto and off of the valve seat in response to pressure from said inlet ports of the valve body and pressure on the seat and thereby allow injection gas to flow upward through the valve port to exit at the upper end of the valve body. A tubular latch is provided with a removable plug to provide for pressure testing and completion of the well with only one wireline trip.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit of and priority to U.S.Provisional Patent Application Ser. No. 61/822,281, filed May 10, 2013,and the contents of which are hereby incorporated by reference in itsentirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

REFERENCE TO APPENDIX

Not applicable.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The inventions disclosed and taught herein relate generally to gas-liftvalves used during both new and existing well completions, and morespecifically are related to gas-lift valve assemblies includingcorrosion-resistant materials and improved flow characteristics withinthe ball assembly, as well as methods of use and manufacture the same.

2. Description of the Related Art

It is common practice to pump lift gas into the annulus between aproduction tubing and surrounding well casing and to pump the lift gassubsequently into the production tubing from the annulus via one or moreone way gas lift flow control devices in side pockets that aredistributed along the length of the production tubing. The lift gaswhich is injected through the flow control devices into the crude oil(or other fluid) stream in the production conduit reduces the density ofthe fluid column in the production conduit and enhances the crude oilproduction rate of the well.

Commercially available gas lift flow control devices typically useone-way check valves which comprise a ball or hemisphere or cone whichis pressed against a valve seating ring by a spring. If the lift gaspressure is higher than the pressure of the crude oil stream in theproduction conduit then this pressure difference exceeds the forcesexerted to the ball by the spring so that the spring is compressed andthe ball is lifted, or moved away, from the valve seating ring and liftgas is permitted to flow from the gas filled injection conduit into theproduction conduit. If, however, the pressure of the crude oil stream ishigher than the lift gas pressure in the injection conduit, theaccumulated forces of the spring and the pressure difference across thegas lift flow control device push the ball or hemisphere against thering shaped seat, thereby closing the check valve and preventing crudeoil, or other fluid, to flow from the production conduit into theinjection conduit.

A problem with the known check valves is that the ball or hemisphere andring-shaped valve seat are exposed to the flux of lift gas, which maycontain liquids or sand or other abrasive particles and/or corrosivechemical components, such as hydrogen sulfide and carbon dioxide. Theball or hemisphere and valve seat are therefore subject to mechanicaland chemical erosion, which may result in leakage of the valve, so thatcrude oil or other fluids may flow into the injection conduit from theproduction conduit, and may block further lift gas injection when thecrude oil, or other fluid, level in the injection conduit has reachedthe location of the gas lift flow control device or flow controldevices.

U.S. Pat. No. 5,535,828 describes a surface controlled gas lift valvewhich is retrievably inserted in a side pocket in the production tubingof an oil well, wherein a frustoconical valve body is mounted on ahydraulically actuated piston which can be actuated from surface topress the valve body against a frustoconical valve seat and to lift thevalve body from the valve seat. The valve body and valve seat areexposed to the flux of lift gas and subject to mechanical and chemicalerosion.

U.S. Pat. No. 5,004,007 describes manners to provide a surfacecontrolled chemical injection valve, wherein a flapper type valve bodyand associated ring-shaped valve seat are protected from exposure to theflux of injected chemicals by a protective sleeve that is pushed byhydraulic pressure through the ring-shaped valve seat and which ispushed back by a spring once the hydraulic pressure has decreased belowa threshold level, thereby permitting the flapper type valve body toswing against the ring-shaped valve seat. The chemical injection valveis equipped with a flow restriction connected to the valve housing and apiston, which is actuated by the pressure difference across the flowrestriction. The piston is arranged in a cylindrical cavity in the valvehousing adjacent to the sleeve and is connected to the sleeve. Thepiston serves to overcome frictional forces between the sleeve and anyseals between the sleeve and valve housing and the presence of thepiston adjacent to the sleeve makes the valve complex, expensive andprone to failure if contaminants, sand or abrasive particles accumulatein the cylindrical cavity above the piston, and/or if the seals fail.

The complex design of the surface controlled chemical injection valverenders it unsuitable to replace the known wear prone spring actuatedball valves.

Gas Lift is the method of artificial lift that uses an external sourceof high-pressure gas for supplementing formation gas to lift the wellfluids. Gas may be injected continuously or intermittently, depending onthe producing characteristics of the well and the arrangement of thegas-lift equipment. Most wells are gas lifted by continuous flow, whichcan be considered an extension of natural flow by supplementing theformation gas with additional high-pressure gas from an outside source.

Gas is injected continuously into the production conduit at a maximumdepth on the basis of the available injection gas pressure. Theinjection gas mixes with the produced well fluids and decreases theflowing pressure gradient of the mixture from the point of gas injectionto the surface. The lower flowing pressure gradient reduces the flowingbottomhole pressure (BHFP) to establish the drawdown required forattaining a designed production rate from the well. If sufficientdrawdown in the bottomhole pressure (BHP) is not possible by continuousflow, intermittent gas lift operation may be used.

Gas-lift is typically achieved by distributing an array of gas-liftvalves along the production tubing string. Optimum flow rate is achievedby having one single injection point as deep in the production tubing aspossible. Typically natural gas is circulated via a compressor to aeratethe production fluid.

Gas-lift valves are typically installed by a latch mechanism in a sidepocket gas-lift mandrel that is attached to the production tubingstring. Tubing and casing pressures cause the gas-lift valve to open andclose, thus allowing gas to be injected into the fluid in the productiontubing from the annulus to cause the fluid to rise to the surface. Suchgas-lift valves inject gas downward into the production tubing.

The early gas lift valves were the conventional type where—by the tubingmandrel that held the gas lift valve and reverse check valve was part ofthe tubing string. It was necessary to pull the tubing to replace aconventional gas lift valve. Selectively retrievable gas lift valve andmandrel combinations have been developed. They provide a valve mandrelwith a pocket, or receiver, within the mandrel from which theretrievable gas lift valve could be removed or installed by simplewireline operations without pulling the tubing.

The primary wireline device for locating the mandrel pocket andselectively removing or installing a gas lift valve is a kick-over tool.The mandrel is called a sidepocket mandrel because the pocket is offsetfrom the centerline of the tubing. Most sidepocket type retrievablevalve mandrels have a full-bore ID equal to the tubing ID. Thesemandrels permit normal wireline operations.

Gas-lift valves utilize a metal bellows and dome attached to a valvestem having a stem tip or ball that moves upward and downward against avalve seat at the opening of a valve port in response to pressure withinthe metal bellows. A gas charge applied to the bellows provides thedownward force, holding the valve tip or ball on the valve seat. The gascharge applied to the bellows is preset as may be desired. A check valve(which is downstream of the stem tip or ball and seat of the valve) isattached to the lower part of the gas-lift valve. The check valve keepsthe flow from the tubing from going back into the casing, i.e., theannulus between the casing and the production tubing.

The gas-lift mandrel serves as a communication port between the casingand the tubing. Gas is injected down the casing into the casing-tubingannulus. The injected gas moves from the annulus to the gas-lift valvethrough communication ports in the gas lift mandrel and inlet ports inthe gas lift valve. The injected gas exits the gas-lift valve downwardinjecting gas against the formation or against the natural flow of thewell.

The opening forces on the valve ball of the gas-lift valve are thecasing pressure acting on the area of the bellows (less the area of thevalve seat) and the tubing pressure acting on the valve seat area. Whenthe combined casing and tubing pressures are sufficient, the valve tipor ball moves upward from the valve seat to open the valve to allowinjection gas to flow through valve port then through the check valve ina downward direction from the gas-lift valve toward the formation. Oncethe valve is open, it remains open until the casing pressure is reducedto the predetermined closing pressure or the tubing pressure or tubingload is reduced.

Gas-lift valves are installed in a gas-lift mandrel with latches such asa BK-2 or BEK-2 latch. These latches are a spring-loaded ring type latchused to secure valves in the gas-lift mandrel. The side pocket mandrelsare in a position with the latch no-go and latch lug facing upward andwith a kick-over tool locator in the upward position.

Typically, once a production tubing string is installed (landed), it isdesirable to test the seal integrity of the whole system or “Completion”assuring there are no leaks in the system. System components beingtested include the packers and gas lift mandrels as well as the pressurecontaining components. During such testing all communication portsbetween the casing or annulus must be sealed off either by closing thedevice or installing a “blank” to replace any sort of circulatingdevice.

In referring to the gas lift system and when a side pocket mandrel isinstalled in the production string, a “dummy valve”, serving as a“blank”, is generally installed in place of the gas lift valve to assurea positive test. Once the whole production tubing assembly has beentested and gas lift operations are needed to lift the well, wirelineintervention is required to remove all dummies and gas lift valves areinstalled. Wireline intervention to change out dummy valves and replacewith live gas lift valves, at minimum, will require two wireline tripsper mandrel to complete the job.

The inventions disclosed and taught herein are directed to gas-liftvalves that have increased life and improved performancecharacteristics.

BRIEF SUMMARY OF THE INVENTION

The objects described above and other advantages and features of theinvention are incorporated in the application as set forth herein, andthe associated appendices and drawings, related to systems for gas-liftvalve assemblies and methods for their use and manufacture.

In accordance with aspects of the invention there is provided a methodof injecting lift gas into a production conduit of an oil well via oneor more downhole gas lift flow control devices which each comprise: atubular valve housing comprising a flow passage having an upstream endwhich is connected to a lift gas supply conduit and a downstream endwhich is connected to the interior of the production conduit; a flappertype valve body which is pivotally connected to the valve housing and isarranged in the flow passage such that if the valve body is pivoted inthe open position the valve body is oriented substantially parallel tothe flow passage and that if the valve body is pivoted in the closedposition the valve body is oriented substantially perpendicular to theflow passage and is pressed against a ring shaped valve seat, therebyblocking passage of fluids through the flow passage; a valve protectionsleeve which is slidably arranged in the flow passage between a firstposition wherein the sleeve extends through the ring-shaped valve seat,whilst the valve body is pivoted in the open position thereof, therebyprotecting the valve seat and valve body against wear by the flux oflift gas or other fluids and a second position wherein the sleeveextends through the section of the flow passage upstream of the valveseat, whilst the valve body is pivoted in the closed position thereof;and a flow restrictor forming part of the valve protection sleeve, whichis dimensioned such that the flux of lift gas or other fluids flowingthrough the flow restrictor creates a difference in pressure whichinduces the sleeve to move towards the first position.

The invention also relates to a gas lift flow control device forinjecting lift gas or other fluids into a production conduit of an oilwell, comprising: a tubular valve housing comprising a flow passagehaving an upstream end which is configured to be connected to a lift gassupply conduit and a downstream end which is configured to be connectedto the interior of the production conduit; a flapper type valve bodywhich is pivotally connected to the valve housing and is arranged in theflow passage such that if the valve body is pivoted in the open positionthe valve body is oriented substantially parallel to the flow passageand that if the valve body is pivoted in the closed position the valvebody is oriented substantially perpendicular to the flow passage and ispressed against a ring shaped valve seat, thereby blocking passage offluids through the flow passage; a valve protection sleeve which isslidably arranged in the flow passage between a first position whereinthe sleeve extends through the ring-shaped valve seat, whilst the valvebody is pivoted in the open position thereof, thereby protecting thevalve seat and valve body against wear by the flux of lift gas or otherfluids and a second position wherein the sleeve extends through thesection of the flow passage upstream of the valve seat, whilst the valvebody is pivoted in the closed position thereof; and a flow restrictorforming part of the valve protection sleeve, which is dimensioned suchthat the flux of lift gas or other fluids flowing through the flowrestrictor creates a difference in pressure which induces the sleeve tomove towards the first position.

In accordance with further aspects of the disclosure, a method andgas-lift valve apparatus is proposed to allow for the injection gas tobe injected from the gas-lift valve upward rather than downward. Theproposed method and gas-lift valve apparatus may be utilized inconjunction with a production tubing string having a plurality of sidepocket mandrels at spaced intervals along the string. Each of thegas-lift valves is operated by available injection pressure or acombination of available injection pressure in conjunction withpressure, within the production tubing at the depth placement of eachgas-lift mandrel.

The method proposes and utilizes a gas-lift valve that prevents downwardflow of injection gas, i.e., toward the well formation, and providesupward flow of injection gas through a latch located at the top of thevalve in the direction of and along with the natural flow of the well.This is accomplished by redirecting the delivery of gas upward throughthe latch. In other valves the injection gas exits at the bottom of thevalve through a check valve. The check valve in the proposed gas-liftvalve is incorporated within the main body of the gas lift valve.

When the injection gas is injected in an upward direction along with thenatural flow of the well, the formation containing the fluids to berecovered is relieved of downward injection pressure. Testing has shownthat reversing the direction of injection gas flow into the productionstring from downward, as is done with prior gas-lift valves, to upwardas described in the proposed gas-lift valve will cause the gas liftedwell to act as if it is flowing on its own. The upward injection of gasfrom the gas-lift valve will eliminate or reduce the eddying effect onthe fluids that occurs in the use of conventional gas-lift valves suchas injection pressure operated (IPO) and production pressure operated(PPO) gas-lift valves. Testing has shown that one may anticipate as muchas a 40% increase in production with the use of the proposed gas-liftvalve in conjunction with gas lift design options.

The proposed gas-lift valve is configured with a body, a gas chargeddome and bellows within the body to manipulate a valve stem and attachedvalve ball on and off of a valve seat. When a combination of the casingpressure from the inlet ports of the gas-lift valve and the tubingpressure on the valve seat reaches or exceeds the nitrogen gas chargewithin the dome and the bellows of the valve, the bellows will collapsemoving the dome downward, causing the valve ball to come off of thevalve seat to allow gas to flow through the port and upward through thecheck valve located in the upper portion of the proposed gas-lift valve,continuing upward through the attached latch. The injection gas thenexits the gas lift valve assembly through the top of the latch.

Redirecting the injection gas upward along with the natural flow of thewell will increase production by adding additional drawdown to theformation. Also injecting gas upward with the natural flow of the wellwill relieve the formation from injection pressures and stabilizing wellflow. Stabilizing the flow of a gas lift well or simulating a naturalflowing well, not only increases production but relieves the wholesystem from stress caused by downward injection. Consequently, theproposed new gas-lift valve and method of gas-lift injection willenhance or increase the production of fluids from the well when comparedto gas-lift valves that injection gas downward in a direction counter tothe natural flow of the well.

This proposed gas-lift valve and method may be in place of most if notall of the gas-lift valves currently being utilized in the industry.This would include by way of example such valves as the Camco-style IPO(Injection Pressure Operated gas-lift valve), the PPO-style (ProductionPressure Operated gas-lift valve), the AT1-BK (Altec Bellows protectedInjection Pressure Operated gas-lift valve), and the AT1-CF-BK (ConstantFlow Injection Pressure Operated gas-lift valve).

The proposed gas lift valve and method is to be used in conjunction witha new flow through latch design, designated as the “EBEK-FT” latch. Thisnew latch will provide a one-hole down-stream choke to the injectiongas. The new latch, configured with a desired sizing of a chokedown-stream of the main port of the gas lift valve, will provide avariety of gas lift design options. The latch will allow the designer touse the down-stream choke to size a desired gas passage required to liftthe well and in turn size the main port, (ball and seat) of the gas liftvalve larger as may be desired. A larger main port (ball and seat) maybe desirable as it will allow more tubing effect in acting to open andclose the valve.

The proposed gas lift valve and method may also be used in conjunctionwith the new flow through latch design in combination with a plug. Thevalve latch and plug combination, designated as the “EBEK-FTD” latch,has all of the benefits as the EBEK-FT latch but will, in addition,provide a removable plug that is installed in the top of the latch. Thisremovable plug may be fitted to the valve and latch combination duringthe initial completion of the well when it is desired to run gas-liftvalves. The plug and latch combination, posing as a dummy valve, willenable testing of the annulus after completion of the well. Once theannulus is tested and the well completed, if gas-lift operations aredesired, only one wireline trip will be required to pull the plug fromthe latch in order to activate the gas-lift valve.

This plug and latch combination will save the consumer from the need topurchase dummy valves and BK-2 latches that would ordinarily have to bereplaced with wireline operations when gas lift operations are requiredin the well. It will also reduce the need for wireline intervention,including the time and risks associated with multiple wireline tripsinto and out of the well.

These and other features, advantages and embodiments of the gas liftmethod and flow control device according to the invention are describedin more detail in the accompanying claims, abstract and detaileddescription with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The following figures form part of the present specification and areincluded to further demonstrate certain aspects of the presentinvention. The invention may be better understood by reference to one ormore of these figures in combination with the detailed description ofspecific embodiments presented herein.

FIG. 1 illustrates a cross-section schematic elevation view of a typicalprior art gas-lift valve.

FIG. 2 illustrates a cross-section elevation view of the gas-lift valveassembly and latch of Applicant's invention as described herein.

FIG. 3 illustrates a partial cross-sectional view of the valve of FIG. 2showing the dome and bellows configuration of the valve assembly in FIG.2.

FIG. 4 illustrates a cross-sectional elevation view of the bellows rodof the value assembly shown in FIG. 2.

FIG. 5 illustrates a cross-sectional view of the latch configuration foruse with the valve assembly of FIG. 2.

FIG. 6 illustrates a cross-sectional view of the latch configuration ofFIG. 5 with a latch plug in place.

FIG. 7 illustrates a side view of a well having mandrels and installedvalves.

FIG. 8 illustrates a cross-section elevation view of the gas-lift valveassembly and latch of Applicant's invention as described herein.

While the inventions disclosed herein are susceptible to variousmodifications and alternative forms, only a few specific embodimentshave been shown by way of example in the drawings and are described indetail below. The figures and detailed descriptions of these specificembodiments are not intended to limit the breadth or scope of theinventive concepts or the appended claims in any manner. Rather, thefigures and detailed written descriptions are provided to illustrate theinventive concepts to a person of ordinary skill in the art and toenable such person to make and use the inventive concepts.

DETAILED DESCRIPTION

The Figures described above and the written description of specificstructures and functions below are not presented to limit the scope ofwhat Applicants have invented or the scope of the appended claims.Rather, the Figures and written description are provided to teach anyperson skilled in the art to make and use the inventions for whichpatent protection is sought. Those skilled in the art will appreciatethat not all features of a commercial embodiment of the inventions aredescribed or shown for the sake of clarity and understanding. Persons ofskill in this art will also appreciate that the development of an actualcommercial embodiment incorporating aspects of the present inventionswill require numerous implementation-specific decisions to achieve thedeveloper's ultimate goal for the commercial embodiment. Suchimplementation-specific decisions may include, and likely are notlimited to, compliance with system-related, business-related,government-related and other constraints, which may vary by specificimplementation, location and from time to time. While a developer'sefforts might be complex and time-consuming in an absolute sense, suchefforts would be, nevertheless, a routine undertaking for those of skillin this art having benefit of this disclosure. It must be understoodthat the inventions disclosed and taught herein are susceptible tonumerous and various modifications and alternative forms. Lastly, theuse of a singular term, such as, but not limited to, “a,” is notintended as limiting of the number of items. Also, the use of relationalterms, such as, but not limited to, “top,” “bottom,” “left,” “right,”“upper,” “lower,” “down,” “up,” “side,” and the like are used in thewritten description for clarity in specific reference to the Figures andare not intended to limit the scope of the invention or the appendedclaims.

Applicants have created improved retrievable gas-lift assemblies, andmethods for their use and manufacture.

Turning now to the figures, FIG. 1 there is shown a cross-sectionelevation view of a gas-lift valve 10 and latch 11 of the conventionalprior art type. The valve to has a metal bellows 12 in communicationwith a gas charge dome 15 at its top. The dome 15 is stationary and hasa constant volume to provide pressure to expand the bellows 12.

The bellows 12 is positioned to manipulate a valve stem 14 positionedbelow the bellows 12. The valve stem 14 has a stem tip or ball 16 thatmoves upward and downward below the bellows 12 against a valve seat 18at an opening to a valve port 20 in response to pressure on the metalbellows 12 from the gas charge dome 15. A predetermined gas charge isapplied to the dome 15 and bellows 12 so as to provide a downward forceon the valve ball 16 to hold it on the valve seat 18 to close the valveport 20. The valve port 20 is in communication with injection gas ports17.

A check valve 22 incorporated into the lower part of the gas-lift valvethat is positioned downstream from and below the valve ball 16, valveseat 18 and valve port 20. The position of the check valve 22 in theseconventional gas-lift valves keeps the flow from the tubing in which thevalve is incorporated from going back into the casing (annulus) andmaintains outward flow of the injection gas down the tubing throughvalve port 20 and gas ports 17 toward the well formation and counter tothe flow of the fluid in the tubing.

FIG. 2 shows a cross-section elevation view of the gas-lift valveassembly 40 and latch 100 of Applicant's invention in accordance withits position in the well. As can be seen in FIG. 2 and FIG. 3, anenlarged partial cross-section view, the valve assembly 40 is comprised,from top to bottom, of check valve housing 42, valve seat housing 44,bellows housing 46, valve core housing 48, and valve nose cone 50. Thecheck valve housing 42 and the valve core housing 48 are adapted toreceive a packing stack assembly, not shown. The gas-lift valve assembly40 is configured to be oriented vertically in the well with the checkvalve housing 42 at the top.

A check valve assembly 52 is mounted within the valve check housing 42.The check valve assembly 52 is comprised of a check spring and washercombination 54 that is biased against a vertically orientated lowercheck valve dart 56. The spring 54 retracts vertically up and down toposition the check valve dart 56 against a lower check valve pad 58. Thecheck valve pad 58 defines the opening of a check valve port 60. Theextension of the check spring 54 will move the valve dart 56 away fromthe valve pad 58 to open the check valve port 60. Compression of thecheck spring 54 will move the valve dart 56 toward the valve pad 58 toclose the check valve port 60.

An injection gas seat assembly 62 is mounted within the injection valveseat housing 44. The injection gas seat assembly 62 is comprised ofinjection gas valve seat 64 having an upper end 63 and a lower end 65.The valve seat 64 defines a vertically extending injection gas port 66.

Extending vertically below the valve seat housing 44 is the bellowshousing 46 has inlet ports 49 positioned for communication with theinlet ports of the mandrel. A bellows assembly 70 is mounted with thebellows housing 46 and is positioned at the lower end 65 of the valveseat 64. The bellows assembly 70 is comprised of an injection gas valveball assembly 68, a bellows adaptor 74 that is removably mounted to thehollow dome 71.

A tubular bellows 72 extends from the base of the dome 71. The lower endof the bellows 72 is mounted on the valve core housing so that the upperwill compress and expand in response to external pressures. A bellowsrod 78 extends from the dome 71 through the valve core housing andbellows 72 to support and guide the dome 71 as the dome moves inresponse to movement of the bellows 72.

The bellows adaptor 74 is preferably threadably mounted to the dome 71so that it may be removed to allow fluid to be inserted through thehollow dome 71 and the bellows rod 78 into the valve core housing 48 sothat it will fill the space between the valve core housing and thebellows. Air in the space the space between the valve core housing 48and the bellows 72 is expelled through a communication port 83 in thebellows rod 78.

The gas valve ball assembly 68 is attached to the bellows adaptor 74which in turn is attached to the dome 71 at its upper end. The valveball assembly 68 is configured to move up and down against the lower end65 of the valve seat 64 as the adaptor 74 moves in response to injectiongas pressure acting against the dome 71 and bellows 72 and tubingpressure at the valve port 66.

As shown in FIGS. 2 and 3, the dome 71 has a bore or port 76 adapted toreceive the hollow bellows rod 78. This bellows rod 78, shown in FIG. 4,is attached to the dome 71 and is slidably received through the valvecore housing 48 that supports the tubular metal bellows 72. In thismanner the bellows rod 78 extends between the dome 71 and the valve corehousing 48 and through the bellows 72.

As shown in FIG. 4, the hollow bellows rod 78 has a through bore 79 anda cross-hole communication port 83 drilled at its top end which ispositioned below the dome 71 and into the bore 79 of the bellows rod 78.Connector area 81 allows for a cold-press connection, or alternatively,a thread connection, to the dome 71.

A gasket 77, which may be made of brass or copper, is provided at theinterface of the dome 71 and bellows rod 78. The gasket 77 serves as aseal between the valve core housing 48 and the dome 71 when the bellows72 is fully collapsed and contracted to provide hydraulic bellowsprotection.

As shown in FIG. 2, a bore 80 in the valve core housing 48 is configuredto slidably receive the hollow bellows rod 78 in response to movement ofthe bellows 72 and dome 71. A one-way valve stent 85 is provided in thevalve core housing 48 at the base of the bore 80 to providecommunication with the bore 80 of the valve core housing 48. The one wayvalve stent 85 provides a means for insertion of gas, preferablyNitrogen, in order to charge the dome 71. The nose cone 50 is attachedto the valve core housing 48 at its base to complete the valve assembly40.

The vertically extending valve core housing 48 provides protection tothe bellows 72 as it also serves as a guide for the bellows rod 78 whenthe bellows rod 78 slides into the bore 80 of the valve core housing 48.This keeps the bellows 72 from twisting or bending out of alignment.This configuration also serves as a stop to limit the total travel ofthe bellows 72 as well as a means or barrier to trap the fluid behindthe bellows 72 when the injection valve is fully open.

FIG. 5 is a cross-sectional view of the proposed flow through latch,designated as the “EBEK-FT” latch, configured for use with the valveassembly 40. The latch 100 is comprised of a hollow latch post 101having an elongated bore 114 that is inserted within a latch body 102.The latch 100 is provided with a latch spring 103 and a latch ring 104.A stop 105 is provided for attachment of the latch 100 to the upper endof the check valve housing 42 of the gas-lift valve assembly 40. Shearpin 106 and roll pin 107 are also provided. The hollow latch post 101and bore 114 allows flow from the top of the valve assembly 40 to exit“upward” along with the natural flow of the well.

As shown in FIG. 6, the latch 100 may also be provided with a removableprong or latch plug 110 and incorporated O-ring seals 111. Thecombination of valve latch 100 and plug 110, designated as the“EBEK-FTD” latch, has all of the benefits as the EBEK-FT latch but will,in addition, provide a removable plug 110 that is installed in the topof the latch. The plug 110 is installed within the latch post 101 andsecured by a brass shear pin 112. An O-ring 108 is placed between thelatch post 101 and the latch stop 105 and an O-ring 109 is also placedat the connection between the valve assembly 40 and latch 100.

The latch 100 may be provided with a “choke” in the bottom of the latchaccomplished by reducing or “choking” the bore 114 at the lower end ofthe latch post 101 to a desired dimension. The upper portion of the bore114 of the latch post 101 may be maintained at a constant size such as⅜″ in diameter. Chokes may be made in a variety of sizes such as ⅛″,10/64″, 12/64″, 16″64″, or 20/64″ by providing a plurality ofcorresponding latch posts 101 each having a bore 114 in a size as may bedesired for a particular gas-lift design. The designer may determinewhether or not to use a latch 100 with a choked latch post or, if sochoked, to select from a variety of chokes simply be using a desiredlatch post 101 having a desired choke dimension of the bore 114. Thepressure shear value of the shear pin 112 selected for use will dependupon the choke size of the latch post 101.

An advantage of a choke downstream from the gas valve ball assembly 68and the gas valve seat 64 of the gas-lift valve assembly 40 in thedirection of the flow of the well is that when the valve is fully openthe pressure drop across the gas-lift valve will be seen at the choke inbore 114 in the lower end of latch 100 so that the valve seat 64 andball assembly 68 will be protected from the flow of any fluids includingsalt water and/or small solids in the fluids that may cut the seat 64 orball assembly 68 and as a result contribute to leakage of the valve.

Operation of Bellows/Gas Lift Valve

A gas lift design is determined from data generated by the wellconditions. This data includes certain well parameters such as theavailable injection pressure from the compressor, back pressure from thewell flow, and temperatures of the formation. This well information isused to determine a Test Rack Opening (TRO) pressure that is used toestablish the pressure inside the bellows 72 of the valve assembly 40.

A gas such as Nitrogen is then used to pressurize the bellows 72. Whenthe bellows 72 is pressurized, the bellows 72 extends to move the dome71 and attached ball assembly 68 upward to position the gas valve ballassembly 68 in contact with the lower end 65 of the valve seat 64. Thecontact of the gas valve ball assembly 68 with the valve seat 64 willclose the valve port 66.

Referring to FIG. 7 the gas lift valve assembly 40 may then be installedin a gas lift mandrel 702 on the surface and run with the productiontubing 704 during completion of the well 700. The gas-lift valveassembly 40 may also be installed by means of a wire, utilizing awireline unit, in a side-pocket mandrel previously installed on thetubing string. It is anticipated that a plurality of gas-lift valveassemblies 40 and gas-lift mandrels 702 will be utilized in a singlewell, as shown in FIG. 7.

If after installation, the hydrostatic pressures in the tubing stringare greater than the pressure (TRO) inside the dome 71 and bellows 72 ofa particular gas-lift valve assembly 40, the bellows 72 of that gas-liftvalve assembly will collapse. When a bellows 72 collapses due to wellconditions, the dome 71 and the attached gas valve ball assembly 68 willmove downward to move the gas valve ball assembly 68 away from the lowerend 65 of the valve seat 64 to open the valve port 66. This will allowinjection gas 706 from the annulus between the casing and productiontubing to be injected to into the fluid column of the production tubingstring.

When the gas-lift valve is in the closed position in the well, the gasvalve ball assembly 68 will be positioned against the valve seat 64.When the valve begins to move to the open position with the gas valveball assembly 68 moving away from the valve seat 64 due to gas pressuresor hydrostatic pressures acting on the outside of the bellows (oroutside of the valve itself), the bellows rod 78 moves in a downwarddirection, thus causing fluid to be pushed up through the hollow bellowsrod 78 to exit the bellows rod 78. When the valve is fully opened, thebellows rod 78 continues to slide down in the extending valve corehousing 48 until the gasket 77 contacts the valve core housing 48 toprovide hydraulic bellows protection.

Use of the gas-lift valve assembly 40 with latch 100 and plug 110 incombination with a gas lift mandrel 702 provides the opportunity toinsert the plug 110 into the top of the latch 100 in order to preventcommunication between the annulus and the inside of the productiontubing 704 which, in essence, will serve the purpose of the dummy valvetypically installed for testing purposes. The plug 110 is installed inthe latch 100 and secured in place by the shear pin 112. The O-ringseals 111, 108 and 109 serve to block communication between the annulusand tubing.

When the assembly 40 and latch 100 are installed in a side pocketmandrel pose as a dummy valve, all conventional operations requiring theuse of a dummy valve may be performed on the well. Only one run with awireline unit is required when it is deemed necessary for the gas-liftvalve assembly 40 to be activated. That run will allow the plug 110 tobe pulled from the top of latch 100 in order to activate the gas-liftvalve assembly allowing for injection of gas 706 upward with the flow710 of the well 700 from the top of the latch 100.

The gas-lift valve assembly 40 and latch 100 in combination with theplug 110 and removal procedure provides significant financial benefitsto the user. This combination and procedure allows the gas-lift valve tobe run on initial completion of the well posing as a dummy valve andthus eliminates the cost of dummy valves and latches on initialcompletion when live IPO valves will be required and reduces oreliminates wireline cost to pull dummies and run live valves.

The proposed combination and procedure also reduces the problems withwireline operations that may occur during the changing out of dummyvalves, for example, dropping dummies or valves or having the wirelineof dummy valve get stuck in the tubing which may result in the need forwireline fishing jobs. The combination and procedure also provides theuser design versatility for the gas lift operation as certain gas-liftvalves may be activated in the string, as desired, depending on theprocedure being done at the time.

It is thought that the gas-lift valve and method of the presentinvention and many of its attendant advantages will be understood fromthe foregoing description. It is also thought that one may make variouschanges in the form, construction and arrangement of the parts of thegas-lift valve assembly, apparatus and method without sacrificing itsmaterial advantages or departing from the spirit and scope of theinvention and that the form described herein is merely an exemplaryembodiment of the invention that is limited only by the followingclaims.

Other and further embodiments utilizing one or more aspects of theinventions described above can be devised without departing from thespirit of Applicant's invention. For example, and as shown in the FIG.8, a carbide ball (or similar feature) 90 can replace check spring andwasher combination 54 and check valve dart 56 shown in FIG. 2 of thedisclosure, such that carbide ball 90 is used in place of the check dart56, and clover-leaf-shaped orifices 92 are bored in the check valvehousing 42 to create flow passages around the carbide ball 90. A carbideball 90 is free floating within the valve check housing 42. The carbideball 90 is free to move substantially vertically up and down to positionthe carbide ball 90 against a lower check valve pad 58 or against theclover-leaf-shaped orifices 92. The check valve pad 58 defines theopening of check valve port 60. The carbide ball 90 is configured tomove up and down in response to injection gas pressure acting againstcheck valve port 60. The injection gas pressure acting against the checkvalve port 60 acting on the carbide ball 90 will move the carbide ball90 away from the valve pad 58 to open the check valve port 60 and intothe clover-lead-shaped orifices 92 to create flow passages around thecarbide ball 90. The use of the carbide ball provides more resistance toerosion, while the creation of the shaped bore passages promote flowaround the ball, thus increasing the working efficiency of the valveassembly and the overall system. The check spring and washer combination54 and check valve dart 56 are more likely to erode over time than thecarbide ball 90.

As a further example, and as shown in FIG. 8, a ball stem assembly 94may replace valve ball assembly 68. Ball stem assembly 94 contains aportion of its substantiality round portion truncated to create asubstantially flat top, while valve ball assembly 68 had a substantiallyround top. The ball stem assembly 94 is configured to move up and downagainst the lower end 65 of the valve seat 64 as the adaptor 74 moves inresponse to injection gas pressure acting against the dome 71 andbellows 72 and tubing pressure at the valve port 66. The use of ballstem assembly 94 provides better flow over the improved truncated topround portion, thus increasing the working efficiency of the valveassembly and the overall system.

Further, the various methods and embodiments of the methods ofmanufacture and assembly of the system, as well as locationspecifications, can be included in combination with each other toproduce variations of the disclosed methods and embodiments. Discussionof singular elements can include plural elements and vice-versa.

The order of steps can occur in a variety of sequences unless otherwisespecifically limited. The various steps described herein can be combinedwith other steps, interlineated with the stated steps, and/or split intomultiple steps. Similarly, elements have been described functionally andcan be embodied as separate components or can be combined intocomponents having multiple functions.

The inventions have been described in the context of preferred and otherembodiments and not every embodiment of the invention has beendescribed. Obvious modifications and alterations to the describedembodiments are available to those of ordinary skill in the art. Thedisclosed and undisclosed embodiments are not intended to limit orrestrict the scope or applicability of the invention conceived of by theApplicants, but rather, in conformity with the patent laws, Applicantsintend to fully protect all such modifications and improvements thatcome within the scope or range of equivalent of the following claims.

What is claimed is:
 1. A check valve assembly for controlling fluid flowin retrievable gas-lift valve apparatus, comprising: a check valvehousing, wherein the check valve housing has a vertically extendingthrough-bore; a substantially spherical body slideably disposed withinthe vertically extending through-bore of the check valve housing; and aseat disposed in a lower portion of the vertically extendingthrough-bore and permitting the fluid flow therethrough.
 2. The checkvalve assembly of claim 1, wherein the substantially spherical body iscapable of substantially free-floating vertical movement within thecheck valve housing.
 3. The check valve assembly of claim 1, where inthe substantially spherical body is a ball.
 4. The check valve assemblyof claim 1, where in the substantially spherical body is a carbide ball.5. The check valve assembly of claim 1, wherein the through-bore of thecheck valve housing comprises clover-leaf-shaped orifices.
 6. The checkvalve assembly of claim 1, wherein the through-bore of the check valvehousing comprises clover-leaf-shaped orifices.
 7. The check valveassembly of claim 6, wherein the clover-leaf-shaped orifices are locatedin its upper portion of the through-bore of the check valve housing. 8.The check valve assembly of claim 6, wherein the clover-leaf-shapedorifices are located above the substantially spherical body.
 9. Aretrievable gas-lift valve apparatus, the apparatus comprising: an upperportion, comprising: a check valve housing, wherein the check valvehousing has a vertically extending through-bore; a substantiallyspherical body located within the vertically extending through-bore ofthe check valve housing; a lower portion comprising: valve seat housing,a bellows housing, and a valve core housing.
 10. The retrievablegas-lift valve apparatus of claim 9, wherein the substantially sphericalbody is a ball.
 11. The retrievable gas-lift valve apparatus of claim 9,wherein the substantially spherical body is a carbide ball.
 12. Theretrievable gas-lift valve apparatus of claim 9, wherein thethrough-bore of the check valve housing has clover-leaf-shaped orifices.13. The retrievable gas-lift valve apparatus of claim 9, wherein thewherein the through-bore of the check valve housing hasclover-leaf-shaped orifices in its upper portion.
 14. The retrievablegas-lift valve apparatus of claim 9, wherein the lower portion comprisesa gas valve ball, wherein the gas valve ball comprises an uppersubstantially round portion, wherein the upper substantially roundportion comprises a flat top.
 15. A method of injecting a gas into aproduction conduit of an oil well, the method comprising: a) installinga gas-lift valve assembly; b) collapsing a bellows of the gas-lift valveassembly when the hydrostatic pressures in the tubing string are greaterthan the pressure inside and the bellows; c) moving a bellows dome ofthe bellows and a gas valve ball of the gas-lift valve assembly downwardand away from a valve seat to open a valve port of a valve assembly ofthe gas-life assembly; d) moving a substantially spherical bodyvertically through a through-bore within a check valve housing of thegas-lift valve assembly; and d) injecting gas from the gas valveassembly into the fluid column of the production tubing string.
 16. Themethod of claim 15, wherein the substantially spherical body is a ball.17. The method of claim 15, wherein the substantially spherical body isa carbide ball.
 18. The method of claim 15, wherein the through-bore ofthe check valve housing has clover-leaf-shaped orifices.
 19. The methodof claim 15, wherein the gas flows through the clover-leaf-shapedorifices.
 20. The method of claim 15, wherein the gas valve ballcomprises an upper substantially round portion, wherein the uppersubstantially round portion comprises a flat top.